使用的fscanf从给定的行读取 [英] Use fscanf to read from given line

问题描述

我想读到有多达10行的txt文件。该文件的格式是这样上的所有行：

  1 1 8
2 2 3
3 1 15
4 2 7
 

我想写将从只传递给它一个int提供的线上阅读功能。我想用一个for循环线路不扫描任何重复，但我无法弄清楚如何实现这一点。

我的功能，至今看起来像这样，for循环尚未实现正常呢。

 无效过程（INT LINENUM，字符*全名）
  {
    INT二，NUM1，NUM2，NUM3;    FILE * F;
    F = FOPEN（全名，R）;    如果（F == NULL）
      {
      的printf（错误：无法打开％S，全名）;
      }    其他
    {
    用于（ⅱ= 0（ⅱ= 0;ⅱ≤（LINENUM-1）;ⅱ++）
      {
      / *通过无扫描线移动* /
      的fscanf（F，％D％D，＆安培; NUM1，＆安培; NUM2，＆安培; NUM3）;
      }    的printf（数字是：％D％d个\\ N，NUM1，NUM2，NUM3）;
    }
  }
 

解决方案

您差不多快完成，但你只需要更改格式specifier.The以下code通过线$ P $读取pceding您的预期线，但忽略它的读取。

 为（ⅱ= 0（ⅱ= 1;ⅱ≤（LINENUM-1）;ⅱ++）
      {
      / *通过无扫描线移动* /
      的fscanf（F，％* D％* D％* D％* C）;
      //的fscanf（F，％* D％* D％* D \\ n）;
      }
的fscanf（F，％D％D，＆安培; NUM1，＆安培; NUM2，＆安培; NUM3）;
 

I want read a txt file that has up to 10 lines. The file is formatted like this on all lines:

1 1 8
2 2 3
3 1 15
4 2 7

I'm trying to write a function that will read from only the line provided by an int passed to it. I thought of using a for loop to iterate through the lines without scanning anything but I can't figure out how to implement that.

My function so far looks like this, the for loop has not been implemented properly yet.

void process(int lineNum, char *fullName)
  {
    int ii, num1, num2, num3;

    FILE* f; 
    f = fopen(fullName, "r");

    if(f==NULL) 
      {
      printf("Error: could not open %S", fullName);
      }

    else
    {
    for (ii=0 (ii = 0; ii < (lineNum-1); ii++)
      {
      /*move through lines without scanning*/
      fscanf(f, "%d %d %d", &num1, &num2, &num3);
      }

    printf("Numbers are: %d %d %d \n",num1, num2, num3);
    }
  }

解决方案

You were nearly done but you simply need to change the format specifier.The following code reads through the lines preceding your intended line,but ignores what it reads.

for (ii=0 (ii = 1; ii < (lineNum-1); ii++)
      {
      /*move through lines without scanning*/
      fscanf(f, "%*d %*d %*d%*c");
      // fscanf(f, "%*d %*d %*d\n");
      }
fscanf(f,"%d%d%d",&num1,&num2,&num3);

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